MARINE ECOLOGY PROGRESS SERIES
Mar Ecol Prog Ser
Published November 2
Deep-sea meiofauna communities in Antarctica:
structural analysis and relation with
the environment
S. ~anhove'v*,
J. Wittoeckl, G. Desmetl, B. Van den ~ e r g h e lR.
, L. erm man',
R. P. M. ~ a k ' G.
, ~ieuwland',J. H. vosjan2,A. Boldrin3,S. ~ a b i t t iM.
~ , vincx1
'University of Gent. Department Morphology, Systematics & Ecology, Section Marine Biology, K. L. Ledeganckstraat 35,
B-9000 Gent, Belgium
' ~ e d e r l a n d sInstituut voor Onderzoek d e r Zee, Postbox 59. 1790 AB Den BurgITexel, The Netherlands
'Institute d i Biologia del Mare, CNR, Riva 7 Martiri 1364/A, 1-30122 Venezia, Italy
ABSTRACT. The metazoan meiofauna in the region off Kapp Norvegia, Antarctica (Weddell Sea; 71" S,
12" \ V ) , was collected from depths between 211 and 2080 m. Total meiofaunal abundance ranged from
815 to 5122 ind. per 10 cm2 and total biomass from 126 to 966 pg dwt per 10 cm2 Nematodes dominated
the samples (range 83 to 9 7 % ) , followed by harpacticoid copepods, polychaetes a n d kinorhynchs. A
typical skewed length frequency distribution was obtained wlth most nematodes in the 0.4 to 0.6 mm
size-class. The meiofauna communities were primarily influenced by bathymetric depth a n d food availability ( e g. organic matter and microbiota), whlch in turn are suggested to be directly related to phytoplankton blooms and associated sedimentation pulses. S t a n d ~ n ystock and distribution patterns indicate that the meiofauna from the Weddell Sea show similar features to major deep-sea assemblages
elsewhere in the world.
KEY WORDS: Meiofauna . Continental margin . Antarctica
INTRODUCTION
The ecology of deep-sea meiofauna has been extensively studied since the first quantitative investigation
by Wigley & McIntyre (1964). Most of these studies,
however, have focused on the Atlantic, Pacific a n d
Indian Oceans (Vincx et al. 1994). So far only 2 meiofauna studies have investigated sediments from deep
polar seas: one in northern boreal waters (Pfannkuche
& Thiel 1987) a n d one in the Weddell Sea, Antarctica
(Herman & Dahms 1992).
Compared to other oceanic regions, the pelagic of
the Southern Ocean (e.g. south of 50" S) has a very
short, but extremely intense, summer phytoplankton
bloom, often associated with the melting of the packice. As benthic communities depend heavily on the
O Inter-Research 1995
Resale of full article not permitted
supply of resources from the water column, the seasonality, intensity and spatial heterogeneity of depositing
matter will certainly affect the size a n d structure of its
components. T h e intense pulse in primary production
results in strong sedimentation of organic matter to the
sea bed (Knox 1994).
From macrobenthic studies it appears that Antarctic
shelf and slope sediments support high biomasses a n d
large numbers of individuals, characterized by a relative
scarceness of infaunal worms. Towards the deep sea (below 1000 m) Antarctic and non-Antarctic biomass levels
d o not seem to differ greatly (Arntz et al. 1994).
Studies on cycling of organic matter in deep-sea sedi m e n t ~of the northeast Atlantic suggest degradation
rates of 0.3 to 2.9% d-' (Lochte 1992). Remineralization processes in the sediment mainly involve bacteria
(Poremba 1994), but meiofauna also play a n important
role (Findlay & Tenore 1982, Ingham et al. 1985, Alkemade et al. 1992, Giere 1993).
Mar Ecol Prog Ser 127: 65-76, 1995
66
The objectives of this study are (1)to assess the composition and population densities of the meiofauna off
Kapp Norvegia, in the Weddell Sea (71 to 72" S, 12 to
13" W) and describe their distribution across the continental margin; (2) to compare the results with a previous study on meiofauna composition in a similar transect in the Weddell Sea to the south and west of the
present study (Herman & Dahms 1992, Halley Bay);
and (3) to relate the benthic structures to events occurring in the overlying water column by comparison with
other deep-sea areas in the world.
This study serves as background for a more detailed
investigation on the meiofauna in the Antarctic environment. In the future, research emphasis will be on
the ecological role of the most abundant and ecologically important taxon, the nematodes.
MATERIAL AND METHODS
Study area and treatment of meiofauna samples
(Fig. 1, Table 1). Samples were collected off Kapp
SHELF-ICE
Norvegia (Weddell Sea, 71 to 72'S, 12 to 13" W ) during
the third leg of the European Polarstern Study (EPOS)
carried out by the RV 'Polarstern' between 13 January
and 10 March 1989).General descriptions of the biological, chemical and physical characteristics of the Weddell Sea during the present investigation are given by
Hempel (1993). Characteristic features of sedimentation, hydrography and topography off Kapp Norvegia
are described in Grobe (1986).The investigated bathymetric range was between 211 and 2080 m. Ice had
started to retreat during the sampling period. The sedlments are of glacial marine and biogenic origin (Hough
1956),and mainly consist of fine sands.
Samples were taken with a multicorer with a hydraulic system (MUC; each core 25 cm2; Barnett et al.
1984). A multiboxcorer (MG; each core 240 cm2;
Gerdes 1990) was used where sampling with the more
fragile multicorer was impossible, because of bad
weather conditions and high sediment gravel content.
The sampling device and original station numbers are
included in Table 1. In both cases meiofauna was subsampled using 10 cm2 plastic cores and rnaterlal was
CONTINENTAL COASTLINE
4 GLACIER
Fig. l . Map s h o w ~ n gthe study area in the Weddell Sea, with station locations
1
,
MG
292
295
MUC MUC
294
K6
"Chloroplastic p ~ g m e n equivalents
t
(chlorophyll a and degradation pr0duct.s)
a s a biomass estimate of bacteria In the sediment
506
313
MG
278
Kapp Norvegla
K3
K4
K5
Eh (mV]
At -1 cm
At 5crn
MG
277
K2
130.8 118.3
103.7 94.6
MG
274
K1
Benthic microbiota (values integrated
over 63 mm) (ng C cm-2)
Heterotrophic nanoflagellates
88.2
Bacteria
Sediment ATP" (mg
(PM)
Pore water n u t r ~ e n content
t
SiOz
p04
NO2
No3
Sedlment pigment content (119
Chl a
Pheo CPE.
C/N
Sediment oraanlc matter
org C
Tot (
Organic matter
Sediment granulometry ('X,)
Mcan ( p h ~ )
Gravel
Very coarse sand
Sand
Silt
Clay
Porosity
I Sampling gear
Depth (m)
Station number
(according to Arntz e t al. 1990)
p
-
Station:
229
H2
MUC MUC
226
H1
MG
230
H3
241
H5
245
248
Halley Bay
H6
H7
249
H8
H9
250
P
252
1-110
253
HI1
MUC MUC MUC MUC MUC MUC MUC MUC
235
-
H4
-
MG
258
p
H12
(
Table 1 Environmental characteristics a t the study sites in the Weddell Sea. Values a r e integrated over the top 5 cm, except where stated. O r i g ~ n a station
l
numbers and
sampling gear employed (MG: multiboxcorer; MUC: multicorer) a r e added
Mar Ecol Prog Ser 127 65-76, 1995
held on a 38 pm mesh sieve. For 6 stations at least
2 cores were analysed for both bathymetric distribution
(SD is spatial distribution, bulk sediment) and vertical
distribution (VD)within the sediment. The detailed descriptions of the VD replicates will be presented later.
Density data presented are concerned with metazoan
meiofauna. A description of the species composition of
the foraminifers is given by Mateu (1992).
Approximately 200 nematodes were collected from
each SD core, while 100 nematodes were used from each
sediment interval for the VD analysis. After mounting
the nematodes in glycerin slides (Seinhorst 1959), the
length and maximum width of each individual were
measured. Assuming a specific gravity of 1.13 and a
dry/wet weight ratio of 0.25, the biomass of nematodes
K1
K2
K3
K4
K5
K6
Station
was calculated using the adjusted method of Andrassy
(Soetaert 1989). Parametric (ANOVA, covariance anFig. 2. Mean meiobenthos densities (no. 10 cm-' * SE) and
alysis) analysis was performed on respectively square
mean total biomass (pg dwt 10 cm-2 i SE) at the 6 stations
and fourth root transformed data of total biomass and
density. Nonparametric analysis (Kruskal-Wallis; Siege1
RESULTS
1956) was used on the data for individual nematode
length and nematode biomass, where the assumptions
Sample replication
for parametric analysis were not met.
Comparison with Halley Bay. Herman & Dahms
The contrast analysis (ANOVA) showed that there
(1992) described the structure of the meiofauna along a
similar depth transect in the Weddell Sea at Halley Bay.
was no significant difference between a VD and an SD
Their results were compared with the current data to
treatment (SD is bulk sediment; VD is the sum of subsequent sediment slices) of the sediment core. The
assess classification techniques (Two-way INdicator
exception was due to the occurrence of a small-scale
Species ANalysis, TWINSPAN, Hill 1979; Group-Average Sorting cluster analysis, GAS, with the Bray Curtis
spatial heterogeneity within a treatment, probably
similarities, Bray & Curtis 1957) using taxon composireflecting patchiness. Consequently VD and SD samtion. The stations off Kapp Norvegia
are denoted with K1 to K6, the stations
off Halley Bay with H1 to H12. The
Nematodes
Harpactico~dcopepods
density data were reduced using a 4 %
rule (e.g. taxa consisting of less than
2 5000
4 % of the total density after elimina4000
tion of the nematodes were excluded),
150
E 3000
4 100
and were fourth root transformed pri2000
or to this analysis (Jongman et al.
1000
1987).The relation with environmental
o
factors was tested usinq- the nonparaKI
~2
station
Station
metric Spearman rank correlation analysis. Environmental data (sediment
60
Polychaetes
properties and microbiota) were obtained simultaneously with similar
sampling devices (Table 1) For details
30
on methods consult Arntz et al. (1990).
Sediment grain size was calculated
using the Wenthworth classification
10
10
(Krumbein & Pettijohn 1938).
'
0
0
Length and biomass of the nematodes
K3
K4
K5
K6
K1
KZ
K3
K4
K5
K6
K1
K2
station
statlon
of Halley Bay were not presented by
Herman & Dahms (1992).A summary of
Fig. 3. Bathymetric distribution of nematodes, harpact~co~d
copepods, polychaetes and kinorhynchs. Values shown are means t SE (n r 4)
these data is presented in Table 3.
B
EL
+
++
+
-C
Vanhove e t al.. Antarctic meiofauna in deep-sea s e d ~ m e n t s
ples could be assigned as replicates (the
data of the VD treatments are not presented here).
69
Table 2.Relative abundance of nematodes, and mean metazoan meiofaunal
abundance of the less abundant taxa (no. 10 c m - 2 )
K1
Distribution and composition of the
meiofauna off Kapp Norvegia
Abundance nematodes 82.5
Other taxa ('X)
2.7
A m.~ h i ~ o d a
Bivalvia
1.0
Bryozoa
Coelenterata
1.0
Cumacea
Echinodermata
Gastrotricha
0.7
Halacaroidea
6.7
lsopoda
Loncifera
Oligochaeta
0.3
Ostracoda
14.7
Porifera
Priapulida
Rotifera
0.3
Tanaidacea
Tardigrada
6.0
Tunicata
Turbellaria
N,. of taxa
8
K2
K3
K4
K5
K6
86.8
96.0
0.5
86.9
3.4
95.9
7.5
3.5
5.0
18
96.4
0.8
0.1
2.0
2.0
.
Total meiofauna densities ranged from
815 * 321.7 ind. 10 cm-2 at 1199 m depth
(K5) to 5122 r 3254.0 ind. 10 cm-' at
537 m depth (K3). Total biomass varied
from 126 k 47.2 pg dwt 10 cm-2 (K4,
561 m) to 966 r 698.6 (K3, 537 m) pg dwt
10 cm-'. The 2 variables were significantly related to each other (dwt: abundance, p i 0.05). Covariance analysis
showed 2 distinct groups of stations
(Tukey, p < 0.001). Stns K1, K2 & K3
(Group I) had the highest densities and
total biomass, while a noticeably lower
stock was found in stations K4, K 5 and
K6 (Group 11) (Fig. 2). There was no clear
relationship with bathymetric depth, but
2 separate geographical groups were
present: Group I was close to the ice-shelf, while
Group I1 was more off-shore. Mean total biomass was
20% higher in Group I than in Group 11. Nematodes
were most abundant, and accounted for 83 to 97 % of
the total. They were followed by nauplii and Harpacticoidea, Polychaeta and l n o r h y n c h a (Fig. 3 ) . The
other taxa (19 in total) comprised together less than
4 % of the total (Table 2). From this table it is clear
that the diversity (number of taxa) did not differ
between Groups I and I1 along the transect. Harpacticoid copepod and polychaete density exhibited a significant negative correlation with depth (p < 0.01),
whereas the nematodes and the kinorhynchs did not
(Fig. 3). The distinction between the ice-shelf and
open-water stations can partly be inferred from the
taxon composition (Fig. 3, Table 2).
I
8.2
9.8
0.8
0.8
0.1
0-4
1.7
1
0.3
0.3
2.0
0.3
0.6
1.8
0.3
1.0
0.5
5.0
8.25
7.2
13.8
1.3
7.8
0.2
0.5
0.2
0.8
1.4
0.8
0.8
0.6
1.7
I
0.2
0.5
3.2
0.2
0.8
1.0
0.3
0.5
6.0
0.3
1.5
0.3
0.5
1.2
1.5
13
0.1
10
9
0.2
0.3
1.0
12
3.3
15
0.1
lengths over 2 and 3 mm respectively. Mean mematode
lengths varied from 743 pm at K4 to 986 pm at K1 (overall mean: 892 pm ? 579; geometric mean: 754 pm;
harmonic mean: 646 pm). The high standard deviation
indicates a high variation between the replicates. Mean
individual nematode lengths were significantly different
Near ice-shelf
Stn K1
r
+
,"
40
""
,,
,
+
,
"
9
9
?
;
-
;
+
9
+++-,+
2
2
9
?
"
v 9' ?: -
zz?x2$$+2?s$
Length-classes (mm)
Offshore
Stn K6
Size structure of nematodes
30
In order to test the hypothesis of Thiel(1975) (i.e.meiofauna become smaller in size with increasing water
depth), nematode sizes were studied along the transect.
The length-frequency distributions of the nematodes in
the 6 stations showed similar shapes. The end stations of
the transect can be considered as representatives for the
whole depth transect (Fig. 4). Skewed patterns were obtained with the
(0.4 to 0.6 mm) being
more highly represented. Only 27% of the nematodes
were longer than 1 mm, and only 4 and 0.9% reached
,,
,,
n
Y
?
x
?
Q
~?
?
~
~-
-
=
xC
!
$
N
L
~
~O
~
r
7
Length-classes (mm)
Fig. 4 Length frequency distributions of the nematodes at
Stns K1 & K 6 o f f Kapp Norvegia (mean length ~n mm + SE, n =
3 a n d 5) Stns K1 & K6 a r e r e ~ r e s e n t a t i v eof the other stations
in
study
tee
s
s
~
$
70
Mar Ecol Prog Ser 127 65-76, 1995
.p
0.1
1
,
I
K1
K2
K4
K3
I
K6
K5
station
Fig 5 Mean l n d ~ v ~ d uba ~l o m a s s( p g dwt r SE) of nematodes
at each statlon oft Kapp Norvegla
between the stations (Kruskal-Wallis, p i 0.001), but
were not related to bathymetric depth. This is consistent
with the overall similarity in a g e structure of the nematodes throughout the transect (53 to 67 % of the organisms were juveniles). The smallest mean individual
nematode biomass per station of 0.140 pg dwt at
K6 shifted to 0.352 pg dwt at K1 (overall mean: 0.233 1-19
~
harmonic mean:
dwt; geometnc mean: 0.07 L I dwt;
0.03 pg dwt, Fig. 5). Mean individual nematode biomass
was significantly different between the stations
(Kruskal-Wallis, p < 0.001) and negatively correlated
with water depth ( p < 0.01).
DISCUSSION
Halley Bay (74 to 75" S; 25 to 29" W) Kapp Norvegia (71 to 72" S; 12 to 13"W)
Meiofauna
Table 3 represents a comparison between the 2
regions in the Weddell Sea studied to date. The nematode community in Kapp N o r v e g ~ adoes not markedly
differ from Halley Bay (Herman & Dahms 1992). Only
slightly higher density a n d biomass readings were
noted in the former area. Similar conclusions can be
drawn from the TWINSPAN analysis (Fig. 6 ) , where no
-E10
K5
K6
Shelf
Halley
. Bay
.
438 m
H9
All
Deeper Slope
Halley Bay
Kapp Norveg~a
1445 m
I
Shelf
Upper slope
-
Kapp Norvegla
501 m
Halley Bay
577 m
Fig 6. TLVINSPAN analysis of the samples based on the
fourth-root-transformed taxon data w ~ t hthe Indicator species
(taxa) for each divis~onl n d ~ c a t e d
clear distinction was found between the 2 transects.
Clusters were primarily made on the basis of bathymetric location and/or distance to the ice-shelf, which
was also relevant from the correlation analysis, and
was also from observations by Herman & Dahms
(1992).A strong resemblance was found between the
following areas: the shelf stations off Halley Bay ( H I ,
H2, H3, H4, H5; mean depth 438 m; indicator species:
polychaetes); the deeper slopes of both transects (K5,
K6, H9, H10, H11; mean depth: 1445 m ) ; the shelf stations off Kapp Norvegia (K2, K3, K4; mean depth
501 m ; indicator species: turbellarians and priapulids);
a n d the upper slope of Halley Bay (H6, H?, H8, H12
a n d exception K1, mean depth 577 m, indicator species: halacarids). Comparable sub-divis~ons were
obtained In the GAS analysis (not depicted), with the
exception that all the shelf stations were clustered in a
single group, and distinctly separated from the deeper
localities (upper a n d deeper slope).
Meso-scale variability in the Weddell Sea
A significant correlation was found between depth
and food (e.g. ATP, organic matter, heterotrophic
Tahle 3 Cornpanson of t h t > maln v a r ~ a b l e sof the nematode c o m m u n ~ t ~ between
es
Halley Bay a n d Kapp Nol8.r-r[ia.Data glven are
the range values at each of the s ~ t e smeans
;
a r e In parenthesch
Halley Bay (582-1958 m)
Absolute d e n s ~ t ,( ~ n dper 10 c n ~)
Relat~vedensity I )
Mean ~ n d ~ v i d ulength
al
(mrril
Mean ~ndividualb ~ o m a s s( p g dwt)
Total b ~ o m a s s( g dwt m - ' )
Kapp Norvegia (211-2080 m )
Vanhove et a1 : Antarctic meiofauna in deep-sea sed~ments
nanoflagellates and bacteria) on one hand, and meiofauna on the other hand (Table 4 ) . Except for
kinorhynch, nematode and oligochaete densities,
meiofauna distribution was not correlated with sediment texture. Surface oxygen levels (Eh), pore water
nutrients ( S i 0 2 ,PO4, NOz, NO3),and pigment concentrations (chlorophyll a, phaeopigments) also had little
impact. High variability between sites was found in the
sediment texture, nutrient pore water chemistry,
microbiota (bacteria and heterotrophic nanoflagellates), and concentrations of pigments and organic
matter (Table 1). Despite this, the sediments within the
4 major TWIN-groups exhibited several abiotic and
biotic similarities (Fig. 7). The shelf of Halley Bay was
typically characterized by high total density, high
numbers of nematodes, kinorhynchs, heterotrophic
nanoflagellates, intermediate nematode biomass values and very low nauplii numbers; the sediments were
a mixture of silt and sand, and contained high ATP and
CPE levels. The shelf of Kapp Norvegia had a dense
meiofauna population, coarser sedirnents a n d high
food concentrations. The deeper slopes of both transects were poor in terms of meiofauna density and
biomass compared to the shelves. Low ATP, CPE a n d
flagellate concentrations characterized the fine sediments. Total density and biomass, nematode density,
and ATP in the upper slope sediments had a strong
affinity with the d e e p localities, where generally intermediate concentrations were found. The sands were
the major component of the sediment, and there was a
significant occurrence of gravels. The sedimentation
patterns can be related to high energy conditions d u e
71
to the effect of the Antarctic Coastal Current in this
zone (Rohardt et al. 1990). Such conditions prevent the
deposition of finer fractions. At about 400 m deep off
Halley Bay (Stns H4, H5, H6) active sedimentation
processes were recognizable from the high values of
total suspended matter observed during the cruise
(Rabitti & Boldrin 1990).
A cluster analysis on macrobenthic densities a n d
biomass in the Weddell Sea region (Galeron et al.
1992) indicated the existence of 2 assemblages according to geographic location (e.g. southern and eastern
shelf communities), though high variability within a n d
between these 2 groups was found. For the same reason Gerdes et al. (1992) could not easily distinguish
macrobenthic biomass from Halley Bay a n d Kapp
Norvegia. Most stations, therefore, were grouped with
the eastern shelf community described by VoI3 (1988),
which is mainly composed of a rich and diverse community of suspension feeders, strongly dependent on
depositing food particles.
Small-scale variability in the sediment
A high variation between replicates (as seen for the
density and biornass of the meiofauna), was observed.
This small-scale (at the cm2 level) heterogeneity, inherent to meiofauna in general (Sun & Fleeger 1991), is
likely to be strongly influenced by the rnicrotopography a n d physical structure of the habitat, a n d hence
the patchy distribution of the earlier mentioned environmental factors.
Table 4. Summary of significant Spearman rank order correlations for meiofauna variables with environmental charactcrlst~cs
measured: total meiofauna density; total nematode biomass; individual nematode biomass; number of taxa; nematodes (Nem.);
kinorhynches (Kin.); harpacticoids (Har.);cnidarians (Cni.); priapulids (Pri.); naupliids (Nau.); oligochaetes (011.); tardigrades
(Tar.);ostracocls (Ost.);tanaidaceans (Tan.); bivalves (Biv.);polychaetes (Pol)
Tot. Tot
Ind.
dens b~oln biom.
Depth
Porosity
Very coarse sand
Sand
Silt
Clay
SiO?
NO3
Eh a t 1 cm
ATP
Organic carbon
Organic nitrogen
Biomass bacteria
B~omassflagellates
Nem. Km.
Har.
Cni.
Prl
Nau.
Tar
Ost.
Tan
Pol
Mar Ecol Prog Ser 127: 65-76, 1995
72
N
=Q
z
3.000
2.500
2.000
1.500
1.000
so0
n
80
Nematodes
a
25
"l 20
=k8
60
20
o
Shelf Halley Bay
Deeper slope Halley Bay
l5
l0
5
n
+
Kapp Norvegia
Shelf Kapp Norvegia
Upper slope Halley Bay
Fig. 7. Sediment characteristics and meiofauna densities in the 4 TWIN groups
Comparison with other deep-sea areas in the world
Meiofauna
Table 5 is restricted to transects crossing continental
shelves and upper slopes (e.g. k200 to 2000 m). The
mesh sizes of sieves were similar, except for the study of
Shirayama & Kojima (1994).As the use of different gear
seriously influences the quantity of meiofauna sampled
(Blomqvist 1991, Bett et al. 1994), only boxcore and
multicore studies were considered. In this context it is
important to note that a mixture of year types was used
in the current study (Table 1). According to Bett et al.
(1994),boxcorers are less efficient collectors result~ng
in lower density records, with possible differences of up
to 50%. However, the apparent bias may vary both
with time and location. From the present study it is d ~ f ficult to test the difference in sampling efficiency as
both types were not applied at the same sites. If such
sample bias occurred, the implication is that density
data obtained from multiboxcorer samples would underestimate the true population levels.
From Table 5 it is clear that the meiofauna in the
Weddell Sea is characterized by densities within the
range of other deep-sea environments (the upper limit
of 5122 ind. 10 cm-' is a single exceptional high value).
Only the warm and oligotrophic deep-sea sediments in
the Red and Mediterranean Sea had significantly
poorer populations. Hence, the current results fit the regression of total metazoan meiofauna density with water depth, calculated for the northeast Atlantic Ocean
(Vincx et al. 1994, Fig. 8).The composition of meiofaunal taxa turned out to be similar to that found in other
deep-sea environments, with a predominance of nematodes and a relatively high importance of harpacticoids,
polychaetes and kinorhynchs. A body mass of 0.05 to
0.14 pg C is also in accordance with dimensions of
deep-sea nematodes recorded from similar depths in
the east Atlantic Ocean and Norwegian Sea (Jensen
1988, Soltwedel 1993) Mean individual dwt diminished
along the transect, but no correlation was found with
median size. This difference is because extremely large
individuals are less frequent at greater depths. These
results partly support Thiel's hypothesis (1975).
Environmental impact
The factors controlling the standing stock of deepsea benthos have recently received more attention.
Vanhove et al.: Antarctic meiofauna in deep-sea sediments
Table 5. Literature data on total metazoan rneiofauna density and biornass in deep seas with comparable depths. Box: (mu1ti)boxcorer; MC: multicorer; 'unicellular organisms included in total counts, "only nematodes counted. Following Heip et al. (1985),
conversion factors of 0.1, 0.4 and 0.5 were used to obtain comparable C equivalents from wet wt, dwt and AFDW respectively
Region
Source
Depth
(m)
Mediterranean Sea De Bovee et al. (1990)
Soetaert et al. (1991),Heip et al. (1985)
Red Sea
Thiel (1979)
Thiel et al. (1987)
Pfannkuche (1993)
Pacific Ocean
Shirayarna & Kojima (1994)
Atlantic Ocean
-NE Atlantic
-NW Atlantic
-SE Atlantic
Norwegian Sea
Arctic Ocean
-Barents Sea &
Nansen Basin
Southern Ocean
-Weddell Sea
672 to 2105
160 to 1220
Gear
Mesh
(pm)
Density
(ind. 10 c m e 2 )
Biomass
(g C m-2)
Box
Box
40
38
36 to 1005
370 to 724
0.002 to 0.028
40
42
40
39 to 407
43 to 195'
33 to 123'
507 to 1977
Box
593 to 1945
Box
1223 to 1650 Mc+Box
245 to 1964
Box
63
438 to 2060'
290 to 2000
500 to 2000
190 to 325
400 to 800
551 to 1965
283 to 2000
970 to 1255
1250 to 2250
Box
MC
Box
Box
Box
Box
Box
Box
42
42
38
42
42
40
45
40
30 to 4226
828 to 2604
864 to 915
217 to 1408'
277 to 1398
139 to 971
138 to 204"
600 to 1920
Pfannkuche & Thiel (1987)
226 to 2500
Box
42
1143 to 4339
Herman & Dahms (1992), this paper
211 to 2080 Mc+Box
38
815 to 5122
Thiel (1971)
Pfannkuche (1985)
Vanreusel et al. (1992)
Coull et al. (1977)
Soltwedel (1993)
Dinet (1974)
Jensen (1988)
Thiel (1975)
Gage & Tyler (1991) stated that large areas of the
deep-sea floor are subjected to spatial and temporal
disturbances on scales ranging from centimeters to
tens of kilometers, and from days to decades or longer.
The amount of biologically utilizable particulate
organic matter settling from the pelagic, in particular,
is a function of sedimentation and degradation rates in
the water column, and determines the amplitude and
Densnies (ind 10 cm-')
3500 1
I
I
I
Regression NE A t z t l c
-
Y r 5837 666 In depth
IP = 0.896
,
lI
II
Depth (m)
Fig. 8 Regression output of rne~ofaunaldensities in the northeast Atlantic according to V ~ n c xet al. (1994). Data from the
Weddell Sea are added ( A ) but not included in the regression
analysis
0.020 to 2.850
0.002 to 0.005
0.055 to 0.134
0.030 to 0.890
0.006 to 0.073
0.040 to 0.480
duration of a benthic response (Lutze et al. 1986, Graf
1989, Gooday & Turley 1990, Sayles et al. 1994, Bak et
al. in press). Meiobenthic biota have been suggested to
be structured by such POC flux and therefore coupled
to phenomena in the pelagic (Shirayama & Kojima
1994, Vincx et al. 1994, Soetaert & Heip in press, Vanreuse1 et al. 1995).
The pelagic regime of the high Antarctic is typically
characterized by sudden and pronounced bloom
events. Substantial amounts of organic carbon and
biogenic opal may sink as a result of high plankton
death rates, current activity and melting processes in
the vicinity of ice-shelves and polynyas (Fischer et al.
1988, Wefer et al. 1990). Moreover, the sedimentation
of faecal pellets originating from the grazing activity
of protozoans, copepods and krill is sometimes the
main process for the transport of material from the
surface to the sea floor in the Weddell Sea (Wefer et
al. 1990). The importance of sedimentation pulses,
both from the bloom and grazing, decrease with
increasing distance from the shelf (Nothig 1988,
Weber 1992). In the coastal/shelf domain off Vestkapp
(Weddell Sea) primary production exhibited high figures in the austral summer, ranging from 100 to
d - l , with a maxlmum daily POC flux
1000 mg C
of 65% at 100 m depth (von Bodungen et al. 1988).
For Kapp Norvegia no data on primary production
74
Mar Ecol Prog Ser 127: 65-76, 1995
were found, but flux rates were 3 to 110 mg m-* d - ' at
630 m (Bathmann et al. 1991).
Substantial transport of phytodetritus to the sea bed
(after ice-cover-related bloom events) and supplementary lateral transport mechanisms were thought to give
rise to high concentrations of CPE in high Arctic waters
(Pfannkuche & Thiel 1987). Low temperatures induce
low microbial metabolic rates, and hence low organic
degradation. Therefore, according to Thiel (1983), food
is available to the benthos for longer periods in these
cold environments. In combination with low benthic
respiration, which is thought to slow down growth rates
and increase individual life spans, these high food concentrations gave rise to high meiobenthic standing
stocks in the Arctic (Pfannkuche & Thiel 1987).
The same could apply to the cold waters (0.4 to l.g°C;
Rohardt et al. 1990) of the study area. In this region about
60 % of phytoplankton derived detritus is mineralized
within 16 d by the microbial community in the pelagic
(Knox 1994). However, phytodetrit'us can deposit relatively rapidly and rates of l00 to 150 m d - ' have been reported (Billet et al. 1983).This result implies that a great
amount of utilizable organic matter still reaches the sea
bed within a few days. Concentrations of pigment and
organic matter recorded in sediments in this study were,
however, low (Table 3). It is likely that the sampling
periods here were not immediately after phytodetrital
sedimentation events. Deposited organic matter had
probably been utilised by the benthic fauna1 assemblages. Under the assumption that primary production
and POM fluxes to the sea bed showed similar features
as in former years (i.e.high and very time-restricted), thls
would imply that benthos respond rapidly and efficiently
to the episodic food supply.
CONCLUSION
Meiobenthic density and biomass data encountered
in the Weddell Sea are comparable to major deep-sea
environments. Features such as very high, but patchy
primary production, with subsequent variable fluxes to
the sea bed, induce small- and meso-scale variability
between and within substrates (e.g. food resources and
sediment texture), and are reflected in meiobenthic
distribution patterns. It seems that the meiofauna in
these regions has, therefore, developed strategies
favourable to the conditions prevalent in deep-sea
environments (e.g. high variability within the environment and unpredictability of food sources). Year round
surveying of meiofauna and sediment properties, and
a detailed investigation of age structure, metabolic
activity and diversity of the populations, is now needed
before further conclusions about the Antarctic deepsea meiofauna can be drawn.
Ackno~vledgernents.The research presented in this paper
was performed under the auspices of the Scientific Research
Programme on Antarctica/ Phase 111 supported by the Belgian
State-Prime Minister's Federal Office for Scientific, Technical
and Cultural Affairs (DWTC],and Institute for the Encouragement of Scientif~cResearch in Industry and Agriculture (IWT).
Samples were collected during the European 'Polarstern'
Study (EPOS), sponsored by the European Science Foundation and the Alfred Wegener Institute for Polar and Marine
Research. Prof. Dr A. Coomans (University of Gent] is
thanked for the research facilities. The authors acknowledge
H.-U. Dahms and Prof. Dr E. Schockaert for their assistance,
Dr Soetaert and J . Schrijvers for their constructive comments,
and Dr L. Peck for corrections of the text.
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This art~clewas submitted to the editor
Manuscript first received: March 13, 1995
Revised version accepted: May 8, 1995